After a wellbore is drilled and completed in a subterranean formation, stimulation operations are usually performed to enhance hydrocarbon production (e.g., oil, gas, etc.) into the wellbore, e.g., by increasing the permeability of the hydrocarbon through the subterranean formation.
A widely used stimulation technique is hydraulic fracturing, in which a fracturing fluid is injected through a wellbore into the surrounding formation at a sufficient pressure to fracture the formation adjacent to the wellbore, creating a fracture network for fluid to flow through the formation back to the wellbore.
Generally, fracturing treatment in a rock formation can create single fractures which extend from opposing sides of the wellbore, i.e., a bi-wing fracture. However, it may not be feasible to create such fractures in many carboniferous formations, such as shales, clays, and/or coal beds. These carboniferous formations typically have finely laminated structures that are easily broken down into pieces. Therefore, creating an effective fracture network in these formations can be an issue.
Efforts have been made to increase cracking of the formations and overall connectivity of the fracture network. For example, diverting agents, such as particulate materials, have been used to block larger fractures in a formation in order to increase permeability of the formation uniformly. However, these diverting systems are typically used near the wellbore and may not be effective to divert treatment fluids to portions of the formation that are significantly distanced from the wellbore. The volume of the formation being treated, therefore, is rather limited.
Another common stimulation technique is acidizing, in which an aqueous acid treatment fluid is introduced into the formation to dissolve acid-soluble materials, e.g., to dissolve materials present in carbonate formations, leaving a desirable amount of voids (e.g., etched fracture, or wormholes) within the formation. This allows hydrocarbon fluids the ability to more easily flow from the formation into the wellbore. Also, acid treatments facilitate the flow of injected treatment fluids from the wellbore into the formation. Conventional diverting systems for the acidizing treatment of carbonate formation may also encounter similar issues to those encountered when implementing hydraulic treatments in shale formations. For example, the volume of the formation being treated is rather limited, often failing to reach locations that are distanced from the wellbore.
Therefore, there is a continuing need in the art for diverting systems that can effectively treat a high volume of subterranean formation, including portions that are distanced from the wellbore.